Li Lianjin

Surface deformation measurements of a finger-joint timber by object-oriented technique and digital speckle image correlation

Digital speckle image correlation technique is a quantized optical experimental method that can accurately determine two-dimensional plane displacements and strains of a target surface. The full-field measurement technique is used in different domains for the study of the mechanical behavior of materials. But the problem has not been solved as yet how the developed programs is used repeatedly or second-developed expediently by other people. In the paper, a program was developed including all digital image correlation calculation programes. Based on the concept of objected-oriented technique in Visual C++ NET, all class libraries of digital speckle image correlation programming were developed and the software system was constructed in order to manage all class libraries. The features of Object-Oriented modeling allow the database to be modeled with the properties of classes, objects, and container trees. Both the portion and all arithmetic in the developed program can be used easily and developed secondly. The programming and reading of was very easy to programming personnel. The programs validity and feasibility was validated by both computer simulation and pull-experiment for a finger-joint timber.

Precision straightening method of thin-walled seamless steel pipes

Discussed are certain calculation issues related to the straightening flattening rate of the six-roll cross-rolling seamless steel pipe straightening mill. Using elastic-plastic straightening theory, the straightening process was deeply analyzed, and then a calculation methodology is developed for the actual straightening flattening rate status of the above-mentioned straightening mill and calculation results for several pipes is compared. Testing results show the actual flattening rate should be the sum of that of theoretical bending and that of straightening. Results put forward to the best method of selecting straightening flattening rate and provide a theoretical basis for improving straightening precision and developing optimal straightening process.

Effect of reduction and temperature on straightening residual stress of seamless pipe

In the process of seamless pipe production, residual stress produced in the straightening process affects the mechanical performance of seamless pipe. Therefore, systematic investigation has been carried out in this paper to find out how residual stress distribution is related to the straightening reduction and temperature in order to meet the tolerance requirements. In the meantime, a detailed analysis on metal flow in the straightening deformation process will be presented to reduce the residual stress by achieving an optimized straightening technology and enhancing the mechanical property. The final results will provide a theoretical foundation for establishing the straightening process.

The semi-active vibration control for building structure by MRF absorber damper

In order, the controlling objective of the minimum structural displacements was aimed to be controlled to improve the comfort of high storey building with the nonlinear characteristics in damping coefficient and rigidity of building structure. The similar model of building structure of three-storey was made based on similarity theory, the 4-DOF vibration system was built up and the parameter of MRF absorber was optimized and designed, while the mass and damping coefficient and rigidity were obtained according to the characteristic of structure; a set of testing system of semi-active vibration control used for building was designed and the effect of damper on shock absorber was studied, under the circumstances of taking the natural frequency and strength of external magnetic field synchronously, swing of structure decreases obviously after fixing the MRF absorber and the vibrating process is reposeful, verifying the effect of MRF absorber on shock absorber.